Electrical leads of the type used with implantable medical devices such as pacemakers and defibrillators utilize a conductor coil having a helical configuration rather than a single straight strand. It is in this context that the present invention will be described.
The joining of elongate articles has long been of concern. For example, U.S. Pat. No. 376,750 to Murphy and U.S. Pat. No. 1,990,077 to Kershaw both disclose solutions for joining pipes. In each instance, an internal sleeve transcends the opposed ends of two lengths of pipe to be joined after which the joint is completed by welding.
The uniting of cable ends of similar diameter is disclosed in U.S. Pat. No. 1,363,355 to Sander, wherein close fitting metallic sleeves are applied to, and preferably flush with, the ends of each cable. Both ends are then inserted into clamps of a butt welding machine by means of which the sleeves and strands are all welded to each other in one composite mass.
In U.S. Pat. No. 3,517,150 to McIntosh et al., axially aligned abutting wires of different diameters are held together by a single coil spring of hard solder wire. The joint is induction heated, fusing the solder to form the junction.
A method of connecting a relatively large diameter, multistrand wire with a relatively small diameter wire is disclosed in U.S. Pat. No. 4,922,072 to Topel et al. First, a portion of the large diameter, multistrand wire is flattened into a body of reduced first transverse dimension and an increased second transverse dimension. Simultaneously, the strands of the body are heat welded into a unitary coherent mass. Second, outer portions of the unitary coherent mass are cut away to reduce the increased second transverse dimension of the mass produced by the flattening step. Finally, the unitary coherent mass is heat welded to the relatively small diameter wire.
It was in light of the foregoing as indicative of the prior art that the present invention was conceived and has now been reduced to practice.